Products made by reduction of quinone compounds using reductases are known to produce reactive oxygen radicals. Reactive oxygen radicals are known to cause oxidative stress, damage DNA and cell membranes, and induce cancer. However, reductases such as quinone oxidoreductase prevent the formation of such free radicals (Anil K. Kaisuwal et al., Biochemical Pharmacology, 60 (2000), 207-214).